Temporal artery biopsy and corticosteroid treatment.

Eighty-four of 132 patients with clinically genuine cranial arteritis had histological evidence of inflammation at temporal artery biopsy. The highest incidence of a positive result (82%) was in patients biopsied before corticosteroid therapy. The figure fell to 60% if corticosteroids had been given for less than a week before biopsy and 10% thereafter.